Focus inductor-furnace



E'. F. NORTHRUP. FOCUS INDUCTOR'FURNACE.

APPLICATION FILED OCT-9,1918.

Patented May 17, 1921.

6 SHEETS-SHEET I.

ATTORNEY Ill /1 E. F. NORTHRUP.

FOCUS INDUCTOR FURNACE.

APPLICATION FILED OCT-9.1918.

Patented May 17,1921.

6 SHEETS-SHEET 2.

FIG. 6. FIG. 7.

E. F. NORTHRUP.

Focus lNDl'JCTOR FURNACE.-.

APPLICATION FILED OCT-9,1918;

Pamntpd May 17, 1921. H 6 SHEETS-SHEET 3.

P V RM m N m R m M 7 WMVIAH M5 E. F. NORTHRUP. FOCUS INDUCTOR FURNACE- APRLICATION FILED OCT 9| 1918.

1,378,187. 1 Patented May 17,1921.

5 SHEETS-SHEET 4. H

FIG. Z].

E. F. N ORTHRUP. FOCUS 'moUcmR FURNACE. APPLICATION FILED OCT. 9, 1918.

m May 17,1921.

6 SHEETS-SHEET 5.

IIIIIIIIIIIIIII A Tram/Er E. F. NORTHRUP,

FOCUS INDUCTOR FURNACE.

APPLICATlON FlLED OCT. 9, 1918.

6 SHEETS-SHEET 6.

FfZZQ.

lullull lmupl mum/70R. 0 W/A/E/VO/FTl/RUP ATTORNEY NE'W JERSEY, 1C CORPURATIGN, QB .wff

'EGCUS INDUGTUZEEUEtHAGlJ.

13"3 D Snecification of Letters Patent.

Application filed flctoher T aZZ whom it may concern Be it known that l, EDWIN f a citizen of the United States, res 30 Wiggins street, Princeton, in the c iuin at Patente -ti May 17, 3132;;

centratlon of energy upon the work by any of a variet of means, of Which ll show two, separately and in combination, the one havmg the distributing end of the inductor of Mercer and State ofNeW Jersey siortened axially and the other having 55 invented a certain new and useiei reduced radially with respect to the receivlnductor-Furnace, of which the following g find Q the iHduCtO-F. is a specification. A further purpose is to pr id a d bl :My invention relates to a translating transformation between a high frequency means by Which high frequency primary primary coil and the u tiinate Wei-lo conto currents in a coil are transformed into elecminer therefor or heat-tran ferring inter-- tric heating currents Within electrically conedi W; that with the Work and, if deducting articles or charges to be heated or sired, both of the transformations heing free Within an electrically conducting container fTOm Who e or partial. interlinlrage of transl5 or other internoediar in heat-transferring former iron. relation to it. further pur ose is to space a fre- FI'Om th ta d i t f l tri al ffiquencyprin and an electrically conductciency it is my purpose to effect th t container, Work or interniediary by a f ti f th hi h lt f th il connect"; loop herein terined an inductor,

to an inductor at a suiiicient distance from rig end forms a secondary to re the work bein heated to permit close cou-- a high -crpiclicy coil whose transmitpling under favorable electrical insulation t ng" or distributing end supplies elecconditions at a moderate temperature and tlCtl e 'y preferably inductivcly .to an to apply the inductor current to the Work, y conducting material or conpreferably also by induction, at so low a 75 voltage as ndt to require good insulation A further purpose is to si lfy the conarfd therefore again to permit close coupling". sti ct-ion of h'grh frequency ducto s and From the standpoint of insulation it is avoid the use of special 2 rials. purpose to place the main electrical insula- A further purpose is to adapt an inductor tion Where the heat can be kept moderate system to high frequency current supply at and to place the heat insulation Where the higher voltages than have previously been potentials of transformation are the same practicable.permitting the use of condensers or their difference 'at least moderate. comprising thick glass plates and feW metal From the standpoint of safety where it sheets suited both to higher vo tages and to 85 is desired to use high tension circuits, it is higher frequencies. f as my purpose to separate the high tension My invention resides hoth in appapart of my system from the work being ratus and in the processes which it disclose. heated so as-to avoid danger of workmen Further purposes will appear in. the ad coming in contact with the high voltage vantages to obtained from the connections 40 current, and to ground the connecting parts and arranger ents show A as to avoid danger from leakage of high ten 1 have i rred to i strate ray invension current thereto. tion Ollie I diagrarnrnatically a l by a few A further purpose is to improve the couonly great var'ety of in which pling between a high frequency primary it may selecting forms which are and the Work. I both s ale and eilicient and which at the so One of the purposes of my invention is sarne t A Well illustrate the principles of to focus or concentrate the energy of the my invention. I inductor upon the Work to which it is Figures 3., 2,;8-15 and are plied. inatic views used in the ition of my to A further purpose is to provide for Fig. 31s a side elevation, partly sectioned, showing structure used in explanation of the theory of my invention.

Fig. 4 is a top plan vlew of the construction seen in'Fig. 2. t

Fig. 5 is a central vertical section, showing appliction of the construction in Fig. 2 to another material.

Figs. 14, 16, 18, 20, 24 and 26 are sections u on line 1414 of Fig.'15; line 1616 of Fig. 17; line l818 of Fig. 19; l1ne20-- -2O of Fig. 21' line Ear-24 of Fig. 25 and line 2626 of ig. 27, respectively.

Figs. 15, 17, 19, 21, 23, 25 and 27 are s de elevationsv of various forms in which my 1nyention may be applied.

Fig. 22 is a top plan vlew of the structure seen in Fig. 23.

Fig. 28 is a horizontal sectlon wlth connections showing a further form of my 1nvention.

Similar numerals of reference indicate like parts in the drawings.

My invention has to do with the transfer of electrical energy through the agency of an inductor from an electric circuit to which high frequency and, if desired, also high voltage currents are applied into heat in electrically conducting materials or charges successively heated, or heat-treated, or in electrically conducting containers or heaters in heat-transferring connection with the material finally to be heated.

Since in all of these materials, charges, containers and heaters alike, electric energy is converted into the heat for whose production the system isintended, they are all regarded as the work heated or treated and are so referred to, for convenience. Obviously, the form may vary widely, as well as the materials.

Perhaps the most convenient application and the one which best illustrates the interchangeability of different forms is the electric furnace where the heat-developing material (always electrically conducting) may be a ferrous or non-ferrous crucible charge or the crucible itself or even a wholly separate conductor having a higher melting point than the charge and placed within the crucible. Because of this fact and because of the success met with in furnace work I have generally illustrated my invention as applied to a crucible furnace and shall illustrate it chiefly in that connection but with knowledge of many other types of furnace and various uses where there is no furnace and v with specific notice that I do not intend to confine or limit it to furnace uses.

In copending applications I have pointed v out a variety of ways in which this transfer pled with the work without interlinkage of a ferromagnetic transformer circuit and hence not requiring the piercing or interruption of the work for this circuit. In all of these the coupling might be regarded as direct, in that the coil was located as close to the work as possible, preferably directly surrounded it, and the work formed the secondary to the high frequency coil as primary.

For many uses the results given by this work-secondary-tohigh-frequency-coil primary proved excellent and this form was sold and successfully used commercially; but for other uses certain objections limited its flexibility and range of application and prevented the fullest development of the principles of my invention. The great difference in potential between the high frequency coil and the work required good electrical insulation where the presence of the highly heated Work limited the character of insulation, increased its thickness and reduced its efficiency. Ionization of the air increased the difficulty.

The energy in the coil could not be concentrated as much as was desirable insome cases upon small masses to be heated. There was also danger, perhaps more seeming than real, of injury to workmen by contact with the coil.

My present invention applies high frequency induced current to the work at a dis tance from the coil, spacing therefrom and forming a coupling, as it were, between the coil and the work whereby the transformation from the primary high frequency'coil, previously coupled directly with the work, is by the present invention coupled through what I have preferred to call an inductor. In its best form a double transformation takes place, the receiving end of the inductor forming a secondary to a high frequency primary coil and the opposite, or distributing end of the inductor forming a primary to which the work is secondary. The transformations at the work end should be made without interlinkage of transformer lron.

The first transformation takes place at a distance from the heat of the furnace, and hence under temperature conditions greatly favoring electrical insulation and permitting the closest of coupling. The second takes place between an extension of the inductor utilized in the first transformation and the work at a ratio of transformation which may, if desired, be made substantially one to one. The low voltage and substantial freedom from electrical insulation requirements permit a closeness of coupling at this point also, not otherwise attainable by reason of the high "temperature.

In other words my present inductor, in its for interlinkage of transformer iron; the one an inductor secondary to the primary high frequency coil and the other an inductor primary to which the work .is a secondary.

The inductor may be and preferably is made to concentrate or focus the energy received from the coil upon the work and is then called by me a focus inductor.

The theory upon which my spacing and preferably focus inductor operates and the reasons for the closeness of coupling which I obtain will be best understood from a consideration of some of the conditions of transfer of energy from a high frequency circuit to an adjoining circuit.

In Fig. 1 a wire primary coil d is shown inside a closed wire secondary coil 1) and in close inductive relation thereto. The application of a high frequency alternating source of electro-motive force 6 to its terminals causes a current 2', to pass through the coil which is represented as momentarily passing in the direction of the arrow. Without necessity for interlinkage of iron there will be an induced current, 71 in the closed coil having an opposite direction and of substantially equal value. here is therefore approximately 100%.

In Fig. 2I have shown the same arrangement except that one of the coils a or 1) comprises a plurality of turns. So far as the number of turns is concerned, the current in b'varies directly as the number of turns in a and inversely as the number of turns in b. In the figure shown, the current 2' willbe approximately equal to nz',:9/i,.

Various commercial embodiments of the construction shown diagrammatically in Fig. 2 have been shown in my previous applications and two are shown herein to illustrate the capability of use of,the sameoper- -ating coils and sources of current supply shown in illustrating my previous invention but applied to carry out my present invention by using my spacing and focus inductors.

In Figs. 3 and 4, I show a high frequency coil A corresponding to the coil a of Fig. 2, but having a different number of turns and fed from any suitable sourceof high frequency current shown diagrammatically. The current passing through the 92, turns of this coil induces a powerful short-circuited current in the single turn or coil ofthe work to which the heat is to be applied, here represented as a'cylinder W.

In the form shown in Fig. 5, high frequency coil A of edge-wound wire surrounds the work VV here shown as comprising either an electrically conducting crucible, or an electrically conducting content M in an electrically non-conducting crucible.

In both of these forms, it will be noted The coupling 'ductors inductively related to these loops,

that the preferably high voltage inductor coil is shown in close proximity to the work which is ultimately to be highly heated. In practice the excessive heat affects the electrical insulation conditions so much that considerable separation of the parts is required.

I have observed one very decided characteristic in which the distribution of alter; nating current differs from the distribution of direct current and which is quite benc-- ficial in the application of my invention.

Whereas in a dividedcircuit, direct current divides so as to reduce the heating effect of the system in its entirety, if the branches 5 be close together alternating current divided. so as to increase the heating efiectfl'. 6., to l111- prove the coupling. This is illustrated by some experiments which I conducted, shown in Figs. 6 to 9 inclusive.

In Figs. 6 and 7 inner and outer wire loops a a are joined at their ends by conductors a, to which any alternating current voltage e is applied. Test strips a a are introduced which, within the intended range, will give visible indication by their color of the comparative temperatures reached.

In the absence of any effect by other con the two conductors a and a will receive ap proximately equal currents, as seen by the colors of the test strips, and so will be heated to approximately the same extent.

When a closed conducting wire, loop or coil 6 is placed in close inductive relation to the inner wire loop the current carried by this loop increases greatly and the current carried by the loop a is correspondingly reduced.

When, instead, a similar closed conducting wire, loop 'or coil 6 is placed in close inductive relation to the outer conductor a instead of to a the reverse is true and the current carried by the outer loop a immediately increases and that carried by the inner loop 0: decreases. When both loops 6 and b are placed in position, the currents carried by a and a again become approximately equal.

From this it will be seen that current induced in the loop I; or b, as the case may be in the opposite direction, reduces the reactance in the adjoining conductor a or ta resulting in an increase in current flow in one or other of these conductors.

correspondingly, when the conductors a and a are replaced by an annulus A as in Figs. 8 and 9, and alternating current is passed through the annulus by reason of the application of an electromotive force 6, the 1 location of loops 6 and b, one at a time, inside or outside of the annulus, results in a corresponding change in distribution of the current flowing through the annulus so as to greatly improve the coupling between.

oc-"o l) is the tlie mirrent in the inner border the loop )art of i border s shown In Fig. 8, Where annulus, a large part oi annulus passes through the thereoi close to the loo 7) outside as in ldigi v the current passe thro l of the annulus close to the-loop, e. by the arrows,

This is true not only of the inducing coil, but in the adjoining conductor, such as represented b or I)", in which the current concentrates along; that sid or edge the conductor closest to the inducing: loop or coil.

Therefore, in addition to some skin effect, Which is present in ell distrioutions of alternating current through condos zinc masses, there is a very marked v of the ur rent so to divide in each vvo conductors in inductive relations e. h increase the current densit in each along that side or border toward b other. greatly increasing the closeness coupling between the inductively members.

lily present invention is directed primarily to the inn roven ent of the coupling between the inducing; coil t7 rou ewhich high frequency currents are passed, which shall call the high frequency coil, and 'nsulation con- (ill.

Work, and to iniprovino the i. ditions. 1 also make it nossible to concentrate or focus the om. I

much smaller surface for duction and of corresponding My invention may he illu inatically b'f; some such for 10: however though this ingg feature which 1t is not of tocusing form.

In Fig". 10 a high frequency current is applied to the terminals of a coil (11 causing a flow ofcurrcnt which in? considered momentarily as passing in direction of the arrow sho'vvn hereon, reversely-olirected current is induced in the coil).

lrlovvever, con if is it shows an 1 t, 1.3 din C) r* n -n l L l us-i in. i, is intcuced o rinzci iioiii i. fact only that the coil 0:. is he e shown as hiring more then one turn, desirably many turns.

in l0 and 11 it will be evident that the coils a, and or m and 72 may he placed very close to each other and the coupling" between may correspondingly he made close, the eillciency approaching 100%, since the. vvorlr heated is spaced from these coils and insulation between is not complicated by any question of temperature. At this the receiving end of the spacing inductor, high frequency current, Whether of high voltage or moderate voltage, may therefore be transformed into low voltage current in the inductor under tee most favorable circurnstunces.

Considering next the distributing end Where the inductor delivers its electric energy into electric current in the work, re sulting in heat therefor, it will be evident that the conditions for closeness of coupling also ideal, since the voltage of the inductor in he made so low that electric insulation between the coil it and the Work may he ignored and the chief, if not the only insulation be that required for the heat.

. lu the work may closely approach 100%, givinc; a maximum of etllciencv.

will be evident also that the inductor d 7 be grounded without interfering; with its operation, protectinu .oni leakage of current "he nigh volt e coil a to the inductor. Ohviously, the high frequency coil (2 and the receiving inductor coil 7) may bear any relation of number of turns to each other that may prove desirable in the design of the apparatus and the distribution coil It may bear any relation of number of turns to the work w that may he desired, keeping in mind, however, that the henetlts of my invention will he reatest hotl. from the standpoint of safety to the workmen and permissible closeness of coupling it the voltage of the inductor be maintained low. will also be clear that the distributing coil 72 will have the same flexibility of upnlication to difiercnt lrinds and shapes of work and outside, inside or any other in ductire relation thereto as would be the with a high frequency coil symbolized or i for example). 12 l have shown a form of the igned to illustrate the benefit oi the division of the alternating current the lines of closest coupling" and the henent of this principle in the application of my invention.

As seen "from the discussion of Figs. 6-9., the presence of the inductor receiving loop letween the high frequency coil and B about the high frequency coil A results in a concentration of the nducing current about the outer shell or surface of the coil A and .of the induced current about the inner shell or surface of the receiving end or coil B of the inductor D. Correspondingly, the presence of the conducting cylinder or crucible, by which the Work W is here illustrated, within the distributing end or coil H causes a distribution of'the induced (now inducing) current within the coil H about its inner shell or surface and of the induced current in the-work W along its outer shell or surface.

In each' case this concentration of current close to 'the'surface greatly reduces the average distance between the lines of travel of the inducing and induced currents, respectivel as compared with the paths which t ey would travel if they spread uniformly over the several conductors. The coupling is thus tremendously impro 'ved for each of the two transformations.

I would particularly point out that m invention is intended for use with big frequency current in which the excessive phase displacement (otherwise caused by the necessarily high reactance) is corrected to the extent desired for the particular installation, by the presence of a condenser, the use of a synchronous converter or other suitable means. This hase adjustment is highly important, both theoretically and practically, and is regarded by me as one of the largest contributing factors in application of this inventionsuccessfully upon any extended scale. I

Though I purpose filing a separate ap plication directed to'this phase correction, I illustrate several forms by which this may be accomplished through the use of condensers or synchronous converters feeding magnetizing current to the line, giving a range from very low to very high voltage, as may be desired and a frequency of thou-. sands of cycles which I consider highly de-" sirable for the purpose.

Some forms of securing high frequencies while maintaining a sufficiently high power factor, notwithstanding the reactance of the circuit, utilize condensers to adjust the phase of the current and tovsecure a current of large voltage range" from the low voltage possible with a generator to thousands of volts. The oscillations secured by these constructions are free as distinguished from those which are forced, and may be damped or undamped as preferred.

In Fig. 13 I show connections of a typical inductor system having transformation at' each end of the inductor and supplied with energy from a condenser whose oscillations are damped.

The condenser y the inductor itself.

C is charged from a source Though the unlaminated character of the work in the case of W (Figs. 3 and 4) and W (Fig. 5) results in free range of eddy currents through the work, considered as a conductor, this is not objectionable because whatever energy is dissipated in eddy currents is converted into heat and this heating of the work is the prime purpose sought. However, in a s acmg or focus "inductor, large unlaminated masses of theinductor become undesirable on account of the dissipation of the ener in eddy currents within Heating of the inductor not only represents a loss of the energy so used but is further objectionable because 1t renders effective insulation more diflicultat the receiving end of the inductor and requires undue spacing there. For this reason, it is very desirable to laminate or otherwise subdivide'the inductor.

Many ways of laminating will occur to the deslgner in view of the information herein given and 1t is not my purpose to attempt to give any more than a suggestion of severa ways in which it may be performed.

-I show stranded conductors whose flexi- In Figs. 14 and 15 Ihave shown a combination of stranded conductors at one end of the inductor and strips or bands at other end thereof, usin the strips or bands at the distributing en The inductor D here shown spacesbut does not focus.

High frequency coil A may evidently be of any type and number of turns and is shown as located inside of the series of superimposed coils forming the receiving end B. of the inductor D The individual coils B are here shown as com rising two turns each of insulated strande cable conductor but may evidently comprise a single turn or any other desired, preferably low, number of turns. They are supported at any suitable number of points by insulating standards J which maintain them in posltion and may be used to spacethem. The terminals of the coils are joined at' some portion in the neck section of the inductor also be supported and, if necessary, spaced by insulating standards J and it is desirable to have the inductor grounded at some point. This may readily be done by a similar standard J of conducting material.

I have shown connectors between the stranded cables and the strips at'K and have interposed between the connectors and the strips short connecting bars K by which two of the strips forming a coil H are electrically connected in parallel.

It will be obvious that the relative sizes of the receiving and distributingends, the characters of the coils there located, the respective axial lengths of the coils, their spacing and the direction of their spacing, whether laterally, axially or' radially'with respect to the high frequency coil, may all begreatlyyaried. It will also be evident that the inductor may becoupled with the high frequency coil andwith the work,

" either by placing the coils outside'or inside the high frequency coil andw'ork or either one outside and the other inside. I have shown some of the varieties which may be used in order to illustrate this fact, without, however, making any attempt at a complete displayof the variety which may exist.

In some uses of my invention it is quite desirable to have the energy delivered by the inductor concentrated effectively or focused upon the work, as, for example, by reducing the diameter or axial length of the coil at the work end of the inductor as compared with the coil at the high frequency or oscillation end thereof.

In Figs. 16 and 17 one means of securing this concentration is shown,-corresponding generally to Figs. 14 and 15 in that the inductor spaces the work laterally from the high frequency coil.

The inductor is shown as made up of a casting D longitudinally kerfed or cut at short intervals to interrupt transverse cur rents and utilize the uncut )ortions as supports for the structure. dditional supports J may be-supplied if desired or entirely separate strips or sections" may be usedas' preferred.

,In this form the current induced by the high frequency coil A in receiving coil B is concentrated upon or within a relatively small volume of work through the distributing loop H of relatively small diameter.

It will be noted that here the general character of strips shown in coils H in Figs. 14 and 15 extend uninterruptedly the entire length of the inductor.

In Figs. 18 and 19 I have shown the same general type of construction as in Figs. 14 and 15 in that stranded cables B are used for the coils B at the receiving end of the inductor but they form sigle turns only and are connected in parallel in groups with bars K from which conductors F lead to groups of coils H in multiple. The conductors areunited to the coils through sockets and bars K as in Figs. 14 and 15.

The coils H are of shorter total axial length than the stranded cable coils at the receiving end of the inductor, resulting in a concentration or focusing of the energy axially upon a shorter length and correspondingly smaller volume of work W In Figs. 20 and 21 the coils and connections forming the inductor are of the same character as in Figs. 18 and 19 except that the distributing coils are of smaller radius as well as of shorter total axial length than those at the receiving end, corresponding in this particular to Figs. 16 and 17. Another difference lies in the greater number of groups into which the receiving coils B are divided, I

The division of the separate coils making up the inductor into parts which are, or may be distinct, as in Figs. 1821, permits multiphase supply to be used, dividing axially, along the same lines. V

In Figs. 22 and 23, I have shown the receiving and distributing-ends of the inductor spaced axially 1t would, of course, make no difi'erencein the operation whether the high frequency coil and receiving end of the inductor be above or below the distributing'end and work. They are shown above? There is the same opportunity here for focusing the energy upon a relatively /small volume of work as in the other forms of the invention and I have illustrated this form as of focusing type, connecting the individual coils B of the receiving end B by means of bars K, in multiple and connecting them by rods F with coils H which are of shorter total axial length and smaller diameter than the receiving coils B It will be noted that the coils at the receiving end are shown as inside the high frequency coil A but could be placed outside, by a very simple rearrangement, as in the other forms, if preferred. The inductor can be grounded as in the other forms.

In Figs. 21-27 the receiving coils B are also conveniently placed inside the high fre-' quency coil A. In both of these forms the distributing end of the focus inductor is smaller in diameter than the receiving end and is coaxial therewith as in the case of Figs. 22 and 23. There is one difference, however, in that the distributing end lies directly within the receiving end in Figs. 2427 and the spacing might therefore aptly be called radia In both of tliese forms the strips or hands forming the inductor are continuous and radially-directed neck parts F F 4 connect the coils B and B with the inner coils II" and "H In the form shown in Figs. 24 and 25 the storing all or a part of the char coils B and H are axially co-extensive while in Figs. 26 and 27 the coil H} is shorter radially as well as smaller in diameter than the outer (receiving) coil B..

In Fig. 28 I have taken advantage of the.

spacing of the focus inductor to place the receiving ends thereof where the workmen cannot accidentally come in contact with them. This is done in the illustration by placing them behind a protecting fence, screen or wall 0 where higher voltage may be safely used upon the high frequency coil and where the coils may be fed in series more safely as shown from a source of current E of much hi her voltage, supplying a condenser c whlch discharges through a gap G.

The distributing ends of the inductors D are located upon the exposed side of the protecting wall where the work may be handled freely without danger to the workman.

The importance of the condensers in adjustment of the phase relation between the current and the electro-motive force and in e, including all which discharges throu the gap and high frequency coil in one orm of my invention, makes any improvement in the condensers of great importance. The tremendous difference in voltage rendered available by this safeguarding of the workman from danger by reason of leakage of the current from the individual high frequency coils and the permissible series arrangement of these coils greatly reduces the number of plates necessary for the condenser and permits the use of thick glass in the condensers, much reducing the expense of the condenser equipment.

A comparison of Figs. 12, 14-21 and 28 with Figs. 3 and 4 shows that any of these inductors having a receiving end of suit- 4 be rigidly secured to the able diameter and axial length can be interchanged with the work W shown in Figs. 3 and 4 to effect spacing and, if desired, also focusing of the cnerg upon a relatively small mass of work. xcept as the type of heat and electrical insulation selected might high frequency coil A or A (Figs. 3 and 5) and thus unduly space the receiving end of the inductor radially from the coil the inductor would also be highly eflicient when substituted for the work in these figures.

Likewise it will be evident that the inductors shown in Figs. 22-27 could be substituted for the work VV shown in Fig. 5 within high frequency coil A or placed within coil A to secure a similar flexibility, whereby the coil is adapted to heat either the work or a spacing and permissibly also focusing inductor.

In l igs.293l I have shown circuit connections taken from my earlier applications (but of which 25) and 31 are modified to show inductors) andnew Figs. 32 and 33,

indicating different power factor corrections. These are a few only of the many connections by which the inductor feature of my invention may be carried out, and indicate that there may be great variety in this and that the invention i independent of the character and source of current used, provided the current be of high frequency and sufficiently near to being in phase with respect to the electromotive force.

In Fig. 29, I have shown a source of alternating current 40 bv which current is supplied to a circuit branching at 41, 42-and including an adjustable excess of capacity, as at 0', in one branch and an excess of inductance over the normal inductance of the circuit.

With the connections shown the current in the circuit including the additional ca:

pacity and inductance will be much in excess of the current in the generator leads, the difference representing storage of energy in the condensers used' and its discharge from them.

The two branches may be tuned or approximately tuned to the frequency of the generator or other source of alternating current su ply to give a freely oscillating current. he heating circuit is illustrated by a coil A", which surrounds an inductor as shown. The coil A supplies a part at least of the inductance of the circuit.

Resistances 1' and r are. reduced to a minimum in the two branches. The constants are balanced to secure at least approximate tuning of the circuit. lVhere the mass of the work is changed. with this form, the capacity is adjusted to maintain the balance.

In this circuit the impulses are maintained in amplitude (1 e., undamped) and are continuous, constantly receiving the impulse necessary to take the place of the energy which would otherwise be lost at each vibration. The inductor shown is that of Figs. 22 and 23.

In Figs. 30 and 31, a different form of oscillatory current supply and application are shown in two general examples in which the oscillations are not of uniform ampli-' tude (i. c. are damped) and are not continuous. The inductor shown in Fig. 31 corresponds to that in Figs. 25 and 26.

In Fig. 30 the current is supplied through the primary 43 of an alternating current transformer, whose secondary 44 charges a condenser c, and the condenser discharges through a gap G having two gaps between two of the solid electrodes, 45, 45 45 and a common electrode 45 of mercury. The third solid electrodeis for multiphase work, but two only are utilized with the connection shown. The discharge gap circuit does not contain the high frequency (oscillation) coil, but is coupled by an ironless transformer 46 generator circuits with.

with an additional circuit containing reversely connected pancake spirals 47, 47' by which any form of work may be heated. Evidently, the furnace crucible and content shown, to which this is well suited because of the low voltage where the coil lies closest 49 to transformer primaries 50, 50', from whose secondaries 51, 51' condensers a, 0 are charged. The condensers discharge through a gap G of the same character as shown in Fig. 30 except that the middle terminal is here utilized, being connected at the junction 51 of the transformer secondaries. The condensers discharge through a helical form of high frequency coil, shown connected at the middle with 51 For conven' ience in illustration, the form of focusing inductor of Figs. 24: and 25 is illustrated.

In Fig. 32 I have shown a heating system in which the phase relation between the current and electromotive force is regulated:

by asynchronous motor operating as a rotary converter.

A single phase alternating current line 52, 53 from a high frequency generator, supplies current through a transformer 54: to the coil A of an inductor of the character shown in Figs. 22 and'23.

Connected to the main conductors 52, 53 is a synchronous motor 55, acting as a rotary converter, which is preferably adapted to run on no load or on a light load and which is to supply magnetizing current to the line.

For clearness I have omitted starting connections or devices for the motor, considering them sufficiently well known.

he field 56 of this motor is energized by an 'exciter 57, in circuit with the field 58 of which is a rheostat 59, here shown as hand-operated. Increasing the field excitation of the synchronous motor advances the phase of the current with respect to the electromotive force and improves the power factor, enabling the power factor to be adjusted, within the designed range, by means of the rheostat. i

This means of power factor regulation is capable of use on multiphase systems of suply as well as upon single phase systemsbetter, so far'as the convenience of starting is concerned-and may be made automatic. One form of automatic system is found in U. S. Patent No. 872,724: to E. M. Gerry, issued December 3, 1907.

A different means of overcoming the lag or displaced phase relation of the current o ythrough a second transformer 60'. A tpangformer primary '62 is thrown across the heating circuit, cooperating with a secondary 63 in circuit with a condenser c to com-- pensate in a rough way for the lag in current. In order to provide adjustability for the compensation to different needs with variation in conditions in the heating circuit an adjustable transformer primary '64 is provided in series with the heating circuit, and this primary is inductively coupled to the same secondary 63 as the primary 62. Adjustment of the primary 64 is provided by contacts 65 and arm 66 connected with the heating circuit. If desired, the windings may be proportioned so as to give what may be likened to an overoompounding action in a non inductive circuit; that is, so that the accelerating influences of the condenser on the current shall more than compensate for an increased lag of the current when its strength is increased, whereby the effective potential is raised, as in U. S. patent to Steinmetz, No. 513,370, issued January 23, 1894.

From the illustrations above, it will be evident that my invention does not reside in "the manner or mechanism by which the high frequency current is generated or supplied but primarily in the application through an.

inductor to the work of a current of high enough frequency to render the employment of ferro magnetic transformer interlinkage unnecessary.

Having thus described my invention, 'what' I claim as new and desire to secure by Letters Patent is: r

1. In electric heating apparatus, an alternating source of current, a condenser adjusting the phase of the current, a coil supplied with current from said source and a spacing inductor receiving induced current from the coil and distributing the current to the work at a distance from the coil.

2. In electric heating apparatus, an alternating source of current, a condenser adjusting the phase of the current, a coil supplied with current from said source and a laminated spacing inductor receiving induced current from the coil through the laminations in multiple, uniting the currents from the laminations and distributing the current to the work at a distance from the coil.

3. In electric heating apparatus, a high frequency alternating source of current, an

70 character shown in Figs. 22 and 23 through one transformer 60 and a non-inductive load" ironless transformer whose primary is supplied therefrom and an inductor having one end thereof comprising the secondary of sald ironless transformer and the other end spaced from the coil and distributing the infrequency coil, free-from whole or partial.

interthreading of transformer iron, current supply therefor, and a spacing inductor havin one end coaxial with'the coil and distributing the current induced therein to the work at the other end.

6. In an electric furnace, an ironless transformer, a free oscillation source of current supply therefor, and an extension of the secondaryof said tfransformer spaced from said secondary an applying the current of said secondary to the work.

7. In electric heating apparatus, a high frequency coil in combination with a spacing inductor having a loop of a single turn at one end in ironless inductive relation with the coil and distributing at the other end to the work at a distance from the coil.

8. In electric heating apparatus, a coil and a source of high tension, high frequency current therefonin combination with a low tension spacing inductor having one end coaxial with the coil, receiving current from it and distributing it to the work'at the other end.

9. In an electric furnace, a coil and a source of high frequency current therefor, in combination with a spacing inductor having a loop at one end receiving induction from the'coil and a conducting crucible at the opposite end to which the inductor is adapted to supply current.

10. In an electric furnace, a coil and a 50 source of high frequency current therefor,

in combination with an inductor havinga receiving end concentric with the coil and in ironless inductive relation with the coil, the inductor distributing the current to the work at a distance from the coil.

11. In an electric furnace, a coil and a source of oscillation current therefor, in combination with an inductor comprisin a number of parts in multiple to avoid ecIdy 60 currents and which are at one end coupled with the oscillation coil, said inductor distributing the current received to the work at the other end.

12. In electric heating, a source of high voltage, high frequency current, a coil con- 5 nected therewith and a low tension inductor, coupling the coil with electrically conducting work spaced therefrom. J

13; In electric heating apparatus, a source of high freqluency current and a coil connected therewit in combination with a spacing inductor having one end in inductive relation with the coil and the other end spaced therefrom and in inductive relation with electrlcally conducting work. i

14. In electric heating apparatus, a high voltage, high frequency source of current and a coil connected therewith, in combination with a low voltage spacing inductor havin one end in inductive relation with the coil and the other end spacedtherefrom and in inductive relation with electrically conducting work.

15. In electric heating apparatus, a .coil and a source of high frequency current I I l I therefor, 1n comb1nat1on with a plurality of receiving and distributing inductor parts,

in inductive relation with said coil and with electrically conductin work.

16. In electric heating apparatus, a coil, a source of high frequency current therefor, an Inductor having one end in inductive relation thereto, the coil having many times as many turns as the end of the inductor, a connecting portion of the inductor and a distributing inductor end in inductive relation to the work.

17. In electric heating apparatus, a coil and a source of high frequency current therefor, in combinatlon with a spacinginductor in. inductive relation with the coil at one end and with the work at the other and laminated at the ends. a p

18. In electric heating apparatus, a coil. and a source of high frequency current j therefor, in combinatlon with a spacin in-' ductor in inductive relation with the 0011 at one end and with the work at the other, laminated at the ends and with laminatedp'arts connected in multiple. 7 11 19, In electric heating, a coil and a source of high frequency current therefor, in com binatlon with a plurality of groups of receiving coils in inductive relation therewith and distributing coils connected with the groups and in inductive relation with the work.,

20. In an electric furnace, a coil, a source of freely oscillating current therefor, an inductor adapted at one end to lie in close inductive relation with the coil and at the other to lie in close inductive relation to the work and divided at one end in planes perpendicular to the axis of the coil to prevent eddy currents.

21. In electric heating apparatus, a coil and a oource of high frequency current therefor, in-combination with an inductor of high frequency current of high voltage, a

coil through whlch the current is passed, a low voltage inductor having one end in inductiverelation to the coil and the other for the work and a. the inductor circuit.

end spaced therefrom and supplying current grounded connection for In electric heating apparatus, .a source of high frequency current of'high voltage,

I so

- ceived by the other.

a coil through which thia current is passed, a low voltage inductor having oneend in inductive relation to the coil and the other end in inductive relation with the work and a grounded connection for the inductor.

24. In electric heating apparatus, a coil and a source of high frequency current therefor, in combination with an inductor having opposite ends of circular section, in inductive relation'respectively with the coil and the work, having the inductive part at the work end laterally separated from the coil end and the coupling with the work free from interlinkage with a ferro-magnetic transformer circuit.

25. An induction coil, a supply of high I frequency current therefor, an inductor having one member coaxial with the coil and free from interlinkage of transformer iron therewith,'a'distributing end applying the induction to the work and a neck connected therebetween. j I "26. A pair of spaced coils, a high frequency source of current inductively coupled with one of the coils, the coupling being free from interlinkage withtransformer iron and connections between the pair of coils to energize on from the induction re- 2'7. An induction coil, in combination with aninductor adapted to fit therein and comprising coaxial, inductive receiving and distributing ends and connecting neck parts therefor. 28. Acoil adapted to receive high frequency currents, in combination with an inductor having circular, laminated, coaxial ends, one being in inductive relation with the coil, and neck pieces joining the ends.

29. In electric heating apparatus, a coil for inductively receiving and distributing electric energy comprising coaxial turns adapted to cooperate with the primary of a transformer and with the work respectively. 30. In an electric furnace, a coil, a source of high frequency cur-rent therefor and an ",inductor having receiving and distributing ends, one of them located above'the other and the receiving end forming a secondary for the coil.

inwardly turned, in combination with a distributing coil coaxial with and lying within the receiving coil and connected in series withithe receiving coil.

. 33. In electric heating apparatus, coaxial coils of different diameter connected in seriesh and comprisigg a single effective turn eac 34. In electric heating apparatus, coaxial coils of different diameter connected inseries, so connected that the current passes through them in opposite directions and spaced to effectively reduce mutual induction.

35. In electric heating apparatus, a coil for inductively" receiving and distributing electric energy, comprising coaxial turns adapted to cooperate with the primary of a transformer and with the work respectively and of different diameter.

36. In electric heating apparatus, coaxial coils of markedly different diameter connected in series and forming parts of different transformer units.

37. In electric heating apparatus, coaxial coils 'of markedly different diameter connected in series and free from interlinkage of transformer iron.

38. In electric heating apparatus, coaxial coils of different axial length connected in series.

39. In electric heating apparatus, coaxial coils in series forming, parts of different transformer units and having markedly different effective surfaces.

40. In an electric furnace, a coil and a source of high frequency current supply, in combination with an inductor having a receiving end in inductive relation with the coil and a distributing end in inductive relation to the work, located coaxially'of the receiving end and at a distance along the axis therefrom, and connections between the two ends.

41. In electric heating apparatus, a coil and a source of high frequency current supply, in combination with a focus inductor having its receiving end in inductive relation with the coil and its distributing end concentrating the current received about a surface of the work markedly smaller than the effective inductive surface of the receiving end.

42. In electric heating apparatus, a coil and a source of high frequency current therefor, in combination with an inductor having opposite ends in inductive relation respectively with the coil and the Workand ductor having spaced ends in inductive re-' lation to the coil and work respectively and the work end of smaller effective diameter than the coil.

44. In an electric furnace,a coil,a' source of high frequency current therefor and having an inductor receiving and distributing ends, one of them located above the other and the receiving end forming a secondary for the coil and having connections between the two ends, the' distributing end being-of smaller effective inductive cylindrical surface than the receiving end thereof.

45. In electric heating, a coil and a source of high frequency current therefor, in combination with a laminated focus inductor receiving current from the coil at one end and distributing it at the other end, the latter having a smaller inducing surface than that presented b the coil.

46.'In an electric urnace, a coil and a source of high frequency current therefor, in combination with an inductor having a single turn at its receiving end in inductive relation to the coil, a distributing end comprising a single turn'adapted to surround the work and free from interlinkage of magnetizable transformer material, and neck connecting parts between the two ends.

4.7. A plurality of coils. connected in series and a source of high frequency current therefor," in combination with separate inductors from said coils comprising, each, a receiving end in inductive relation with the coil and a distributing end at a distance therefrom and in inductive relation with the work.

48. A plurality of coils connected in senes .and a source of high frequency current therefor, in combination with separate inductors from said coils comprising, each, a receiving end in inductive relation with the coil and a distributing end at a distance therefrom adapted to supply current to the work.

49. In electric heating apparatus, a coil,

a source of high frequency current therefor of high voltage, a spacing protector in front of said coil and an inductor having a receiving end in inductive relation with the coil, lcoated on one side of the protector and a distributing end for heating the work, located on the opposite side thereof.

50. In electric heating apparatus, a coil, a source of high voltage high frequency current therefor, a spacing protector, and an inductor having a receiving endin inductive relation with the coil, located on one side of the protector and having a distributing end in inductive relation with the work, located on the oppbsite side thereof.

51. In electric heating apparatus, a coil, a source of high voltage, high frequency current therefor, a spacing protector and a focus inductor having a recelving end in inductiverelation with the coil, located on one side of the protector and having a distribut ing end of smaller effective inductive surface than the coil inductively coupled with the work and located upon the opposite side thereof.

52. In an electric heating apparatus, a

primary coil and a source of high frequency current therefor, in combination with a grounded spaclng inductor having inductive relation with the said primary coil at one end and with the work at the other.

53. The process of safe larding the use of a high frequency coil or inducing current in electrically-conducting work without interlinkage of a ferro magnetic transformer circuit therewith, which consists in spacing the work from the coil and connectin the two by an inductor performing the unc-- tions of a secondary to the coil and, without interlinkage of a'ferro-m'agnetic transformer circuit, of a primary to the work as secondary.

54. The process of improvin the closeness of coupling between a high v0 tage coil and work coupled therewith, free from interlinkage of a ferro-magnetic transformer circuit, which consists in removing the work far enough from the coil to prevent undue heating of the latter, connecting'by an inductor of low voltage, thus freeing the insulation between the high voltage coil and the inductor from complication by excessive heat and coupling thev inductor with the work'mductively, at the low voltage, free current in transposing the energy of a.

high voltage, high fequency current passed through a coil into eat in the work, which consists in spacing the coil and work'from each other, changing the high Voltage of the coil into low voltage of an inductor at a point of relatively low temperature and in changing the low voltage inductor current.

into current in the work at the oint of high temperature and in mechanical y separating the'high frequency coil side of the inductor i from possible interference by the workmen.

56., The process of protecting the work.

and workmen from leakage of high voltage current in transposing the energy of a high perature spaced therefrom and in grounding the inductor.

57. The process of focusing the energy of a current of high frequency Within a coil upon a relatively small mass of Work to be heated, Which consists in interposing an inductor having a relatively large surface to receive the induction from the coil and a relatively small surface to distribute the induction to the Work.

58. J'Fhe process of concentrating the induction of a current of high frequency Within a coil upon the Work, which consists in coupling the coil to one end of an inductor, forming the other end of the inductor of smaller effective inductive surface as a primary and coupling it with electrically-con ducting Work to induce the energy in a rela tively small mass of Work.

59. The process of focusing the energy of a freely oscillating current Within a will. upon Work to he heated, which consists in connecting the coil with the Work by an inductor in inductive relations with both and having a smaller effective lnductive sun avage? face in the portion inductively connected with the'Work than the effective inductive inductor performing secondary functions tothe coilfias primary at one end and primary functions to the WOIk as secondary at the other end and having shorter axial length at the .work end than the axial length of the coil.

61. The process of focusing the energy of a current of high frequency Within a coil upon a relatively small mass of electricallyconducting Work, Which consists in coupling the coil to the Work by an inductor having inductive relation With both and of smaller diameter at the Work end than the diameter of the coil.

62. The process of focusing the energy of a current of high frequency Within a coil upon a relatively small mass of electricallyconclucting Work Which consists in coupling the coil to the Work by an inductor having inductive relation With both and'of shorter axial length and smaller diameter at the Work end than the axial length and diameter of the coil.

EDWIN FITCH NORTHRUP. 

